CN114583180A - Composite current collector and preparation method thereof - Google Patents

Composite current collector and preparation method thereof Download PDF

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Publication number
CN114583180A
CN114583180A CN202210267400.3A CN202210267400A CN114583180A CN 114583180 A CN114583180 A CN 114583180A CN 202210267400 A CN202210267400 A CN 202210267400A CN 114583180 A CN114583180 A CN 114583180A
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current collector
modified
substrate
binder
collector substrate
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CN114583180B (en
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王凯
谭立波
熊珊
朱昌波
易靖宇
高夜军
阮祝华
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Hubei Eve Power Co Ltd
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Hubei Eve Power Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0411—Methods of deposition of the material by extrusion
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/049—Manufacturing of an active layer by chemical means
    • H01M4/0492—Chemical attack of the support material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/668—Composites of electroconductive material and synthetic resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/80—Porous plates, e.g. sintered carriers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Cell Electrode Carriers And Collectors (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention provides a composite current collector and a preparation method thereof, wherein the composite current collector comprises a current collector substrate with a surface containing hydroxyl and a modified adhesive layer arranged on at least one side surface of the current collector substrate, the modified adhesive layer comprises a modified adhesive, the surface of the modified adhesive comprises modified polyacrylonitrile, the modified polyacrylonitrile is connected with hydroxyl and/or carboxyl, and the current collector substrate is a porous current collector substrate. According to the invention, the porous current collector substrate with the surface containing hydroxyl is matched with a specific modified binder for use, and the hydroxyl and/or carboxyl contained in the surface of the binder can not only generate acting force with the hydroxyl on the surface of the current collector substrate, but also can act with a negative active material, so that a bridge effect between the current collector and the active material is achieved, the stripping force of a pole piece is further enhanced, the problem of powder falling or lithium precipitation after long circulation of a conventional current collector is solved, the internal resistance of a battery cell is reduced, and the energy density of the battery cell is improved.

Description

Composite current collector and preparation method thereof
Technical Field
The invention belongs to the technical field of batteries, and relates to a composite current collector and a preparation method thereof.
Background
With the promotion of strategic objectives of 'carbon peak reaching' and 'carbon neutralization' in China, the development trend of new energy automobiles is irreversible, and lithium batteries have attracted wide attention as important parts of the new energy automobiles. Besides the four main materials of the lithium ion battery, the auxiliary materials also play a key role in the performance of the lithium ion battery. At present, the foil material for the negative electrode of the lithium battery is a conventional smooth copper foil or a carbon-coated copper foil, and the two types of foil materials can basically meet the performance requirements of the conventional lithium ion battery.
CN104409696B discloses a method for preparing a positive electrode plate of a lithium iron phosphate battery using an aqueous binder and a carbon-coated conductive aluminum foil current collector, wherein slurry is coated on the surface of the carbon-coated conductive aluminum foil current collector to obtain a finished electrode plate, the preparation method is non-toxic, harmless, environment-friendly and safe, and the raw material price is low. CN112820853A provides a pole piece and battery, this pole piece includes the mass flow body and range upon range of the carbon coating layer, active material layer and the protective layer that sets up in proper order on at least one surface of the mass flow body, and the battery that adopts this pole piece preparation has better security performance. CN108493455A discloses a multifunctional lithium battery current collector and a preparation method thereof, the lithium battery current collector comprises a metal foil and multifunctional material layers covering the upper and lower surfaces of the metal foil, the metal foil is an aluminum foil, a copper foil, a carbon-coated aluminum foil or a carbon-coated copper foil, and various foils can be selected as the current collector, so that the prepared battery has high safety performance.
In the prior art, a conventional copper foil or a carbon-coated copper foil is generally adopted as a current collector, but with the gradual improvement of the requirement of the market on the endurance mileage of a new energy automobile, the current collector also puts forward a higher requirement on the cycle performance of a lithium ion battery. The increase in the number of cycles leads to greater cyclic expansion of the negative electrode, and the negative electrode active material is likely to fall off from the current collector during the reciprocating expansion and contraction, and it is difficult to suppress the occurrence of this with the current conventional copper foil current collector. In the later cycle period, the negative active material falls off from the current collector, which can lead to the accelerated attenuation of the capacity of the battery core, the reduction of DCIR, and even the occurrence of lithium precipitation, thus affecting the safety of the battery.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a composite current collector and a preparation method thereof. According to the invention, the porous current collector substrate with hydroxyl on the surface is matched with a specific modified binder for use, and the hydroxyl and/or carboxyl on the surface of the binder can not only generate acting force with the hydroxyl on the surface of the current collector substrate, but also can act with a negative active material, so that a bridge effect between the current collector and the active material is achieved, the stripping force of a pole piece is further enhanced, the problem of powder falling or lithium precipitation after long-term circulation of a conventional current collector is solved, the internal resistance of a battery cell is reduced, and the energy density of the battery cell is improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a composite current collector, which includes a current collector substrate with a surface containing hydroxyl groups and a modified binder layer disposed on at least one side surface of the current collector substrate, wherein the modified binder layer includes a modified binder, the modified binder includes modified polyacrylonitrile, the modified polyacrylonitrile has hydroxyl groups and/or carboxyl groups connected thereto, and the current collector substrate is a porous current collector substrate.
According to the invention, a specific current collector substrate and a specific modified binder are matched for use, and hydroxyl and/or carboxyl contained in the surface of the modified binder can not only generate acting force with hydroxyl on the surface of the current collector substrate, but also can act with a negative active material, so that a bridge effect between the current collector and the active material is achieved, and the stripping force of a pole piece is enhanced. By using the copper foil, the stripping force of the negative pole piece can be obviously enhanced, the problem of powder falling or lithium precipitation after long circulation of the conventional current collector is solved, the internal resistance of the battery cell can be reduced, and the energy density of the battery cell is improved.
On the other hand, the current collector substrate is a porous current collector substrate, the surface of the current collector substrate is in a pore structure, the roughness of the surface of the current collector can be enhanced, the mechanical interlocking effect between an active substance and the current collector is enhanced, and the current collector substrate and the modified binder have synergistic effect to achieve the purpose of enhancing the stripping force; meanwhile, the surface pore-forming of the current collector substrate can reduce the surface density of the current collector substrate, and the energy density of the battery cell can be further improved while the stripping force is improved; the three-dimensional pore structure can improve the contact area of the active substance and the current collector, reduce the resistivity, convert the diffusion path of lithium ions into three-dimensional all-dimensional penetration, and increase the contact surface of the anode and cathode materials and the current collector by adding slurry into pores in the coating process, thereby reducing the migration radius of the lithium ions and improving the conductive efficiency.
Preferably, the porous current collector substrate comprises etched copper foil, wherein the surface of the etched copper foil is in a pore structure and is formed by electrochemical etching, the pore diameter is 0-10 mu m, and pores are distributed on the surface of the current collector.
As a preferred technical solution of the composite current collector of the present invention, the modified binder is LA136S 1.
The preferable modified binder is polyacrylonitrile binder LA136S1 with hydroxyl and carboxyl on the surface, can be combined with the hydroxyl on the surface of the current collector substrate and acts with the negative active material, so that the stripping force and the cycling stability of the pole piece are improved, and the modified binder belongs to a negative binder and cannot influence a negative system; meanwhile, the composite current collector has excellent adhesive force and conductivity and lower internal resistance, and can be used for obtaining a composite current collector with more excellent electrochemical performance under the synergistic action of the composite current collector and the current collector substrate.
Preferably, the thickness of the modified adhesive layer is 1 to 2 μm, and may be, for example, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, or the like.
Illustratively, in the invention, the modified binder is mixed with deionized water to prepare slurry, and then the slurry is uniformly coated on the surface of the porous current collector substrate in an extrusion coating mode, so that hydroxyl and/or carboxyl on the modified polyacrylonitrile binder is combined with hydroxyl on the surface of the porous current collector substrate to generate binding force, the stripping force of a pole piece is enhanced, the problems of powder falling or lithium precipitation after long circulation of a conventional current collector are solved, the internal resistance of a battery cell is reduced, and the energy density of the battery cell is improved
In a second aspect, the present invention provides a method of manufacturing a composite current collector according to the first aspect, the method comprising:
and chemically etching the current collector substrate to obtain a current collector substrate with a surface containing hydroxyl, and coating the surface of at least one side of the current collector substrate with modified binder slurry to obtain the composite current collector.
According to the invention, a chemical etching method is adopted to generate a pore structure on the surface of the current collector substrate, so that the roughness of the current collector substrate is enhanced, the mechanical interlocking effect between an active substance and a current collector is enhanced, and the stripping force of a pole piece is enhanced; meanwhile, a specific modified binder is coated, so that binding force is generated between the current collector substrate and the binder, the stripping force of the pole piece is further enhanced, the problem that the lithium is separated out after the current copper foil current collector is circulated for a long time is solved, and the circulation stability of the pole piece is improved.
As a preferred technical scheme of the preparation method, the chemical etching is carried out according to the following steps:
and placing the current collector substrate in etching liquid for hydrothermal reaction, and performing acid leaching on the current collector substrate after the hydrothermal reaction to obtain the current collector substrate with the surface containing hydroxyl.
The hydrothermal reaction in the invention can adjust the size and the density of the holes, and the etched copper foil suitable for different scenes is obtained.
Preferably, the thickness of the current collector substrate is 7 to 9 μm, and may be 7 μm, 7.5 μm, 8 μm, 8.5 μm, or 9 μm, for example.
Preferably, the surface oil film is removed from the current collector substrate before use. For example, the process of removing the surface oil film from the current collector substrate may be performed by sequentially ultrasonically cleaning the current collector substrate with acetone, absolute ethyl alcohol and deionized water to remove the surface oil film, and then naturally drying the current collector substrate at room temperature, so as to perform subsequent processing.
Preferably, the etching liquid comprises an oxidizing agent and an alkali liquid.
Preferably, the oxidizing agent comprises a sodium persulfate solution, the alkali solution comprises ammonia water, and the etching solution is a mixed solution of sodium persulfate and ammonia water, wherein the volume ratio of the sodium persulfate to the ammonia water is 1: 1.
Preferably, the temperature of the hydrothermal reaction is 140 to 160 ℃, and may be 140 ℃, 145 ℃, 150 ℃, 155 ℃ or 160 ℃, for example.
Preferably, the hydrothermal reaction time is 25-35 min, for example, 25min, 28min, 30min, 32min or 35 min.
According to the invention, the size and the density of the holes can be regulated and controlled by adjusting the time and the temperature of the hydrothermal reaction, the current collector hole effect obtained by the optimal hydrothermal reaction time and temperature is optimal, the synergistic effect of the modified binder is best, and the prepared composite current collector has better electrochemical performance.
After the hydrothermal reaction of the current collector substrate, the current collector substrate can be taken out and washed by absolute ethyl alcohol, and the subsequent operation is carried out after the current collector substrate is naturally dried.
Preferably, the acid leaching solution is hydrochloric acid, and the acid leaching can extract oxides on the surface of the current collector substrate to form a pore structure.
Preferably, the acid leaching time is 15-25 min, for example, 15min, 18min, 20min, 22min or 25 min.
The chemical etching method is simple and effective, and the prepared porous current collector substrate with the surface containing hydroxyl has better comprehensive performance.
As a preferred technical solution of the preparation method of the present invention, the modified binder slurry is prepared as follows:
and mixing the modified binder and the solvent, heating, stirring, cooling and sieving to obtain the modified binder slurry.
Preferably, the solvent comprises deionized water.
Preferably, the mass ratio of the modified binder to the solvent is 1 (15-25), and may be, for example, 1:15, 1:18, 1:20, 1:22, or 1: 25.
Illustratively, the process of mixing the modified binder and the solvent is as follows: stirring the modified binder and the solvent in a mass ratio of 1 (15-25) for 25-35 min, wherein the revolution speed is 15-25 rpm, and the dispersion speed is 750-850 rpm;
illustratively, the process of heating and stirring is as follows: keeping the temperature at 40-50 ℃, adjusting the revolution speed to be 20-30 rpm, adjusting the dispersion speed to be 1400-1600 rpm, and stirring for 115-125 min.
The modified binder slurry is coated on at least one surface of the current collector substrate by extrusion coating.
In a third aspect, the invention provides a negative plate, which comprises the composite current collector according to the first aspect and a negative active material layer arranged on at least one side surface of the composite current collector, wherein the single-side surface density of the negative plate is 45-50 g/m2。
In the invention, the single-sided surface density of the negative plate is 45-50 g/m2For example, it may be 45g/m2、46g/m2、47g/m2、48g/m2、49g/m2Or 50g/m2And the like.
Preferably, the anode active material layer includes an anode active material, a conductive agent, and a binder.
Preferably, the binder comprises CMC and/or LA136S 1.
The negative active material layer is preferably arranged on the surface of the composite current collector and can interact with hydroxyl and carboxyl on the surface of the composite current collector, so that the binding force of the active material layer and the current collector is enhanced, the binding force is tighter, the lithium ion migration path is reduced, and the stripping force and the electrochemical performance of the negative plate are further improved.
In a fourth aspect, the invention provides a lithium ion battery, and the negative electrode of the lithium ion battery adopts the negative electrode sheet according to the third aspect.
The lithium ion battery prepared by the invention has good electrochemical performance.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, a specific current collector substrate and a specific modified binder are matched for use, and hydroxyl and/or carboxyl contained in the surface of the modified binder can not only generate acting force with hydroxyl on the surface of the current collector substrate, but also can act with a negative active material, so that a bridge effect between the current collector and the active material is achieved, and the stripping force of a pole piece is enhanced. The copper foil can obviously enhance the stripping force of the negative pole piece, solve the problem of powder falling or lithium precipitation after long circulation of the conventional current collector, reduce the internal resistance of the battery cell and improve the energy density of the battery cell.
Drawings
Fig. 1 is an SEM image of an etched copper foil prepared in example 1 of the present invention.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a composite current collector and a preparation method thereof, the composite current collector comprises an etched copper foil with a surface containing hydroxyl groups and a modified adhesive layer arranged on one side surface of the etched copper foil, the thickness of the modified adhesive layer is 1.5 mu m, and the modified adhesive layer comprises a modified adhesive LA136S1 with a surface containing hydroxyl groups and carboxyl groups.
The embodiment also provides a preparation method of the composite current collector, which includes:
(1) preparation of etched copper foil: taking a copper foil with the thickness of 8 microns, sequentially carrying out ultrasonic cleaning by using acetone, absolute ethyl alcohol and deionized water to remove an oil film on the surface, and then naturally airing the copper foil at room temperature; preparing a mixed solution of sodium persulfate and ammonia water in a volume ratio of 1:1 as an etching solution, soaking the copper foil with the oil film removed in the etching solution, reacting at a high temperature of 150 ℃ in a hydrothermal reaction kettle for 30min, taking out the copper foil after the reaction is finished, cleaning the residual solution on the surface by absolute ethyl alcohol, naturally drying, soaking for 20min by hydrochloric acid, and removing surface oxides to obtain an etched copper foil with hydroxyl on the surface, wherein an SEM (scanning electron microscope) diagram of the etched copper foil is shown in figure 1, and a hole structure of 0-10 mu m appears on the surface of the copper foil, so that the contact area of an active substance and the copper foil is increased to enhance the stripping force and the conductive efficiency, but the hole does not penetrate through, and the material leakage phenomenon during single-side coating in the coating process is avoided;
(2) preparing a composite current collector: mixing LA136S1 (aqueous binder/available from Yindingle company) and deionized water in a stirring kettle at normal temperature, wherein the mass ratio is 1:20, stirring for 30min, the revolution speed is 20rpm, and the dispersion speed is 800 rpm; then starting heating, keeping the temperature at 45 ℃, adjusting the revolution speed to be 25rpm, the dispersion speed to be 1500rpm, and stirring at the constant temperature of 45 ℃ for 120 min; and (2) naturally cooling the stirred glue solution to room temperature, sieving to obtain a standby glue solution, uniformly coating the standby glue solution on the surface of the etched copper foil prepared in the step (1) in an extrusion coating mode, wherein the coating thickness is 1.5 mu m, and drying at the constant temperature of 40 ℃ to obtain the composite current collector.
The embodiment also provides a negative plate and a preparation method thereof, and the preparation method comprises the following steps:
(1) uniformly mixing CMC and deionized water in a stirring kettle at normal temperature to prepare a negative pole glue solution with the solid content of 1.5 percent for later use;
(2) mixing graphite and conductive carbon black (SP) in a mass ratio of 96:1.8 in another stirring kettle, and stirring for 60min, wherein the revolution speed of the stirring kettle is 20rpm, and the dispersion speed is 500 rpm; and (2) adding a certain amount of the negative pole glue solution prepared in the step (1) and LA136S1 into a stirring kettle, and stirring for 120min, wherein the CMC: the mass ratio of LA136S1 is 0.4:1.8, and negative pole slurry is obtained;
(3) adding a certain amount of deionized water into the negative electrode slurry prepared in the step (2), stirring for 120min, wherein the revolution speed of a stirring kettle is 20rpm, the dispersion speed is 1500rpm, finally preparing the negative electrode slurry with the solid content of 46%, uniformly coating the negative electrode slurry on the prepared composite current collector by adopting extrusion coating, drying at 90 ℃ to prepare a dry negative electrode sheet, and stirring the negative electrode sheet and the composite current collector for 120minThe sheet had a single-sided areal density of 48g/m2。
Example 2
The embodiment provides a composite current collector and a preparation method thereof, the composite current collector comprises an etched copper foil with a surface containing hydroxyl groups and a modified adhesive layer arranged on the surface of one side of the etched copper foil, the thickness of the modified adhesive layer is 2 microns, and the modified adhesive layer comprises a modified adhesive LA136S1 with a surface containing hydroxyl groups and carboxyl groups.
The embodiment also provides a preparation method of the composite current collector, which includes:
(1) preparation of etched copper foil: taking a copper foil with the thickness of 7 microns, sequentially carrying out ultrasonic cleaning by using acetone, absolute ethyl alcohol and deionized water to remove an oil film on the surface, and then naturally airing the copper foil at room temperature; preparing a mixed solution of sodium persulfate and ammonia water in a volume ratio of 1:1 as an etching solution, soaking the copper foil with the oil film removed in the etching solution, reacting at a high temperature of 140 ℃ for 35min in a hydrothermal reaction kettle, taking out the copper foil after the reaction is finished, cleaning the residual solution on the surface by absolute ethyl alcohol, naturally drying, soaking for 15min by hydrochloric acid, and removing the surface oxide to obtain the etched copper foil with the surface containing hydroxyl;
(2) preparing a composite current collector: mixing LA136S1 (aqueous binder/available from Yindingle company) and deionized water in a stirring kettle at normal temperature, wherein the mass ratio is 1:20, stirring for 30min, the revolution speed is 20rpm, and the dispersion speed is 800 rpm; then starting heating, keeping the temperature at 45 ℃, adjusting the revolution speed to be 25rpm, the dispersion speed to be 1500rpm, and stirring at the constant temperature of 45 ℃ for 120 min; and (2) naturally cooling the stirred glue solution to room temperature, sieving to obtain a standby glue solution, uniformly coating the standby glue solution on the surface of the etched copper foil prepared in the step (1) in an extrusion coating mode, wherein the coating thickness is 1.5 mu m, and drying at the constant temperature of 40 ℃ to obtain the composite current collector.
The embodiment also provides a negative plate and a preparation method thereof, and the preparation method comprises the following steps:
(1) uniformly mixing CMC and deionized water in a stirring kettle at normal temperature to prepare a negative pole glue solution with the solid content of 1.5 percent for later use;
(2) mixing graphite and conductive carbon black (SP) in a mass ratio of 96:1.8 in another stirring kettle, and stirring for 60min, wherein the revolution speed of the stirring kettle is 20rpm, and the dispersion speed is 500 rpm; and (2) adding a certain amount of the negative pole glue solution prepared in the step (1) and LA136S1 into a stirring kettle, and stirring for 120min, wherein the CMC: the mass ratio of LA136S1 is 0.4:1.8, and negative pole slurry is obtained;
(3) adding a certain amount of deionized water into the negative electrode slurry prepared in the step (2), stirring for 120min, wherein the revolution speed of a stirring kettle is 20rpm, the dispersion speed is 1500rpm, finally preparing the negative electrode slurry with the solid content of 46%, uniformly coating the negative electrode slurry on the prepared composite current collector by adopting extrusion coating, and drying at 90 ℃ to prepare a dry negative electrode sheet, wherein the single-side surface density of the negative electrode sheet is 50g/m2。
Example 3
The embodiment provides a composite current collector and a preparation method thereof, the composite current collector comprises an etched copper foil with a surface containing hydroxyl groups and a modified adhesive layer arranged on the surface of one side of the etched copper foil, the thickness of the modified adhesive layer is 1 μm, and the modified adhesive layer comprises a modified adhesive LA136S1 with a surface containing hydroxyl groups and carboxyl groups.
The embodiment also provides a preparation method of the composite current collector, which includes:
(1) preparation of etched copper foil: taking a copper foil with the thickness of 9 microns, sequentially carrying out ultrasonic cleaning by using acetone, absolute ethyl alcohol and deionized water to remove an oil film on the surface, and then naturally airing the copper foil at room temperature; preparing a mixed solution of sodium persulfate and ammonia water in a volume ratio of 1:1 as an etching solution, soaking the copper foil with the oil film removed in the etching solution, reacting at 160 ℃ for 25min in a hydrothermal reaction kettle, taking out the copper foil after the reaction is finished, cleaning the residual solution on the surface by absolute ethyl alcohol, naturally drying, soaking for 35min by hydrochloric acid, and removing the surface oxide to obtain the etched copper foil with hydroxyl on the surface;
(2) preparing a composite current collector: mixing LA136S1 (aqueous binder/available from Yindingle company) and deionized water in a stirring kettle at normal temperature, wherein the mass ratio is 1:20, stirring for 30min, the revolution speed is 20rpm, and the dispersion speed is 800 rpm; then starting heating, keeping the temperature at 45 ℃, adjusting the revolution speed to be 25rpm, the dispersion speed to be 1500rpm, and stirring at the constant temperature of 45 ℃ for 120 min; and (2) naturally cooling the stirred glue solution to room temperature, sieving to obtain a standby glue solution, uniformly coating the standby glue solution on the surface of the etched copper foil prepared in the step (1) in an extrusion coating mode, wherein the coating thickness is 1.5 mu m, and drying at the constant temperature of 40 ℃ to obtain the composite current collector.
The embodiment also provides a negative electrode and a preparation method thereof, wherein the preparation method comprises the following steps:
(1) uniformly mixing CMC and deionized water in a stirring kettle at normal temperature to prepare a negative pole glue solution with the solid content of 1.5 percent for later use;
(2) mixing graphite and conductive carbon black (SP) in a mass ratio of 96:1.8 in another stirring kettle, and stirring for 60min, wherein the revolution speed of the stirring kettle is 20rpm, and the dispersion speed is 500 rpm; and (2) adding a certain amount of the negative pole glue solution prepared in the step (1) and LA136S1 into a stirring kettle, and stirring for 120min, wherein the CMC: the mass ratio of LA136S1 is 0.4:1.8, and negative pole slurry is obtained;
(3) adding a certain amount of deionized water into the negative electrode slurry prepared in the step (2), stirring for 120min, wherein the revolution speed of a stirring kettle is 20rpm, the dispersion speed is 1500rpm, finally preparing the negative electrode slurry with the solid content of 46%, uniformly coating the negative electrode slurry on the prepared composite current collector by adopting extrusion coating, and drying at 90 ℃ to prepare a dry negative electrode sheet, wherein the single-side surface density of the negative electrode sheet is 45g/m2。
Example 4
The same procedure as in example 1 was repeated, except that the thickness of the modified adhesive layer was 0.5. mu.m.
Example 5
The same procedure as in example 1 was repeated, except that the thickness of the modified adhesive layer was 2.5. mu.m.
Example 6
The procedure is as in example 1 except that the temperature of the hydrothermal reaction is 120 ℃.
Example 7
The procedure is as in example 1 except that the temperature of the hydrothermal reaction is 180 ℃.
Example 8
The procedure of example 1 was repeated, except that the hydrothermal reaction was changed to room temperature (25 ℃ C.).
Comparative example 1
The comparative example used a conventional copper foil, i.e., the copper foil was not chemically etched, and the surface thereof was not provided with a modified adhesive layer, and the remainder was the same as in example 1.
Comparative example 2
The comparative example used a conventional copper foil, i.e., the copper foil was not chemically etched, and the surface thereof was not provided with a modified adhesive layer, and the remainder was the same as in example 2.
Comparative example 3
The same as example 1 was performed except that the operation of step (1) was not performed in the method for preparing a composite current collector, that is, the conventional copper foil was directly used without performing chemical etching on the copper foil.
Comparative example 4
The same as example 1 except that the preparation method of the composite current collector does not perform the operation of the step (2), i.e., the surface of the etched copper foil is not provided with the modified binder layer.
Comparative example 5
The procedure was as in example 1 except that the modified binder LA136S1 was replaced with CMC.
Comparative example 6
The procedure was as in example 1 except that the modified binder LA136S1 was replaced with sodium polyacrylate.
First, physical property test of copper foil
The etched copper foils or the non-copper foils in the examples and comparative examples of the present invention were subjected to tests of areal density, roughness and tensile strength, wherein the areal density test: testing by using a weighing method, and testing roughness: testing by means of a Focal Station three-dimensional surface topography measuring system, wherein the tensile strength test comprises the following steps: the results obtained using the universal tensile testing machine are shown in Table 1.
Second, testing the stripping force of the cathode plate
The negative electrode sheets in the examples and comparative examples of the present invention were subjected to a peel force test: the electrode plate is divided into strips, a 3M-VHB double-sided adhesive tape is attached to the surface of an electrode, the other surface of the electrode plate is attached to a stainless steel plate, the stainless steel plate and a current collector are fixed on two clamps of a universal tensile testing machine, then a sample is stretched at a certain speed, a 180-degree stripping test is carried out, the force detected when the copper foil current collector is completely stripped is the stripping force, and the test results are shown in Table 1.
Third, resistivity test of negative plate
The negative electrode sheets in the examples and comparative examples of the present invention were subjected to resistivity test: the resistivity meter was used for the test, and the test results are shown in table 1.
Fourthly, testing the electrochemical performance of the lithium ion battery
The negative plate in the embodiment and the comparative example of the invention is used as a negative electrode, lithium iron phosphate is used as a positive electrode, a lithium ion battery is assembled by using electrolyte with a conventional formula, the high-temperature cycle performance of the lithium ion battery is tested, the test voltage interval is 2.0-3.7V, a 3C/3C high-temperature cycle test is carried out until the capacity is attenuated to 80%, and the test results are shown in Table 1.
TABLE 1
Figure BDA0003552369400000131
Figure BDA0003552369400000141
It can be known from the above examples 1 to 8 that, in the invention, the current collector substrate having hydroxyl on the surface is used in combination with a specific modified binder, and the hydroxyl and/or carboxyl on the surface of the binder can not only generate an acting force with the hydroxyl on the surface of the current collector substrate, but also can act with a negative active material, thereby playing a role of a bridge between the current collector and the active material, further enhancing the stripping force of a pole piece, solving the problem of powder falling or lithium precipitation after long-term circulation of a conventional current collector, reducing the internal resistance of a battery cell, and improving the energy density of the battery cell.
As can be seen from the comparison between the embodiment 1 and the embodiments 4 to 5, the modified adhesive layer of the invention has proper thickness on the surface of the current collector substrate, and in the thickness range, the modified adhesive layer has good comprehensive performance, when the thickness is higher, the resistivity is larger, and when the thickness is lower, the adhesive force is poor; thus, the overall performance of example 1 is slightly higher than examples 4-5.
As can be seen from comparison between the embodiment 1 and the embodiments 6 to 8, the etched copper foil obtained by the hydrothermal reaction etching at 140-160 ℃ has the best effect, the synergistic effect of the etched copper foil and the modified binder layer is also the best, when the hydrothermal temperature is higher, the etching condition is serious, the toughness of the current collector is affected, and when the hydrothermal temperature is lower, the etching effect cannot be achieved, so that the comprehensive performance of the embodiments 6 to 8 is slightly lower than that of the embodiment 1.
As can be seen from the comparison between the embodiment 1 and the comparative example 1 and between the embodiment 2 and the comparative example 2, the etched copper foil with the surface containing hydroxyl groups is prepared by adopting a chemical etching mode and is matched with a specific modified binder layer for use, and the stripping force of the negative plate can be improved and the comprehensive electrochemical performance of the lithium ion battery can be improved under the synergistic effect of the etched copper foil and the specific modified binder layer; the comparative examples 1 and 2 both adopt conventional copper foils, the surfaces of which do not contain specific functional groups or modified binder layers, the roughness is lower, the surface density is higher, the stripping force of the negative plate is poorer, the resistivity of the negative electrode is higher, and the lithium ion battery is not favorable for maintaining better cycle stability and higher capacity, so the comprehensive electrochemical performance of the examples 1-2 is far higher than that of the comparative examples 1-2.
It can be known from the comparison between the embodiment 1 and the comparative examples 3 to 6 that the specific current collector substrate and the specific modified binder are not available, the copper foil in the comparative example 3 is not chemically etched, the surface of the copper foil has no pore structure or hydroxyl, the bonding force between the copper foil and the modified binder is weak, and the copper foil cannot generate strong interaction with the negative active material; the modified binder layer is not arranged in the comparative example 4, the modified binder layer lacks a bridge between the modified binder layer and a negative active material, and the stripping force of a pole piece cannot be effectively improved, while the binders adopted in the comparative examples 5 and 6 do not have strong acting force for combining with the hydroxyl on the surface of the copper foil, and the effect is far inferior to that of the invention, so that the comprehensive performance of the composite current collector prepared in the example 1 and the electrochemical performance of the lithium ion battery prepared by the composite current collector are higher than those of the comparative examples 3-6.
The above description is only for the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the protection scope and the disclosure of the present invention.

Claims (10)

1. The utility model provides a composite current collector, its characterized in that, composite current collector includes that the surface contains the mass flow body substrate of hydroxyl and sets up the modified binder layer of the at least one side surface of mass flow body substrate, including the modified binder in the modified binder layer, the modified binder includes modified polyacrylonitrile, modified polyacrylonitrile has connect hydroxyl and/or carboxyl, the mass flow body substrate is porous mass flow body substrate.
2. The composite current collector of claim 1, wherein the porous current collector substrate comprises etched copper foil.
3. The composite current collector of claim 1 or 2, wherein the modified binder is LA136S 1.
4. The composite current collector of any one of claims 1 to 3, wherein the modified binder layer has a thickness of 1 to 2 μm.
5. A method for preparing a composite current collector according to any one of claims 1 to 4, characterized in that it comprises:
and chemically etching the current collector substrate to obtain a current collector substrate with a surface containing hydroxyl, and coating the surface of at least one side of the current collector substrate with modified binder slurry to obtain the composite current collector.
6. The method of claim 5, wherein the chemical etching is performed according to the following steps:
placing the current collector substrate in etching liquid for hydrothermal reaction, and performing acid leaching on the current collector substrate after the hydrothermal reaction to obtain a current collector substrate with a surface containing hydroxyl;
preferably, the thickness of the current collector substrate is 7-9 μm;
preferably, the surface oil film of the current collector substrate is removed before use;
preferably, the etching liquid comprises an oxidizing agent and an alkali liquor;
preferably, the oxidizing agent comprises a sodium persulfate solution, and the lye comprises ammonia;
preferably, the temperature of the hydrothermal reaction is 140-160 ℃;
preferably, the time of the hydrothermal reaction is 25-35 min;
preferably, the acid-leaching solution is hydrochloric acid;
preferably, the acid leaching time is 15-25 min.
7. The method according to claim 5 or 6, wherein the modified binder slurry is prepared as follows:
mixing the modified binder and the solvent, heating and stirring, cooling and sieving to obtain modified binder slurry;
preferably, the solvent comprises deionized water;
preferably, the mass ratio of the modified binder to the solvent is 1 (15-25).
8. A negative plate, characterized in that the negative plate comprises the composite current collector of any one of claims 1 to 7 and a negative active material layer arranged on at least one side surface of the composite current collector, and the single-side surface density of the negative plate is 45-50 g/m2。
9. The negative electrode sheet according to claim 8, wherein the negative electrode active material layer comprises a negative electrode active material, a conductive agent, and a binder;
preferably, the binder comprises CMC and/or LA136S 1.
10. A lithium ion battery, characterized in that the negative electrode of the lithium ion battery adopts the negative electrode sheet according to claim 8 or 9.
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